Building sprinkler systems are designed to provide pressurized water to extinguish fires during emergency situations. A pump is used to provide the necessary water pressure. These pumps are typically powered by an electric motor, however many are often powered by internal combustion engines. The present invention relates to internal combustion engine systems only.
Such sprinkler systems are designed for a defined flow rate and pressure. For a given engine/pump combination, the discharge line pressure, from the pump, is dependent on the fluid flow rate through the system and the pressure of the water being supplied to the pump (called suction pressure). The pressure of the water at the pump suction often has a wide range between its high and low resulting in an equally wide contribution to pump output pressure variances. At a constant engine/pump RPM (Revolutions Per minute). The line pressure will increase as the fluid flow rate decreases through the system. Further, at a fixed throttle setting, as the fluid flow rate decreases, the load on the engine also decreases resulting in an increase in engine rpm, thereby further increasing pressure produced by the pump (this is referred to as the engine droop). The net effect is to increase the pressure, which a sprinkler system must be able to withstand. This basically means stronger more expensive sprinkler system components including water pipes, fittings and sprinklers. Sprinklers are rated for specific operating pressures. This establishes the limits of the system pressures. Some types of sprinklers are further limited to smaller more specific pressure ranges further limiting system pressure ranges.